Support of large rock caverns in Norway

The Gjovik Olympic Mountain Hall has a rock cover of 25-50 m and a span of 61 m. This is by far the largest span ever used for a cavern that is open for public use. The paper reviews the development of tunnelling and the use of the underground in Norway as a background for the decision to build this recordbreaking cavern. Experience from the excavation of very large mining chambers was of crucial importance. The Norwegian approach to the support of tunnels and underground openings is discussed. Excavation and support of large caverns such as hydropower facilities, oil storages and sports halls are described. The support system for the Gjovik. Olympic Mountain Hall is described in detail, and measurements performed on rock bolts and in the shotcrete are discussed. There are clear indications that the total stability of the cavern is primarily a result of favourable horizontal stresses. The majority of the 6-m-long and 12-m-long grouted rock bolts seem to carry very low loads over only Mort lengths of the bolts.